1. Field of the Invention
The invention relates to a magnetic transducer and a thin film magnetic head using the same and more particularly to a magnetic transducer and a thin film magnetic head which can obtain the more excellent rate of resistance change.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an improvement in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive effect (hereinafter referred to as an MR element) that is one of magnetic transducers and a recording head having an inductive-type magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
The reproducing head using the AMR element is called an AMR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 gigabit per square inch, and the GMR head is used as the reproducing head whose surface recording density exceeds 3 gigabits per square inch.
As the GMR film, a xe2x80x9cmultilayered type (antiferromagnetic type)xe2x80x9d film, an xe2x80x9cinductive ferromagnetic typexe2x80x9d film, a xe2x80x9cgranular typexe2x80x9d film, a xe2x80x9cspin valve typexe2x80x9d film and the like are proposed. Of these types of films, the spin valve type film is the GMR film which is considered to be relatively simple in structure, to exhibit a great change in resistance even under a low magnetic field and to be suitable for mass production.
FIG. 22 shows the structure of a general spin valve type GMR film (hereinafter referred to as a spin valve film). A surface indicated by reference symbol S in the drawing corresponds to the surface facing a magnetic recording medium. This spin valve film has the stacked structure comprising an underlying layer 91, a soft magnetic layer 92 made of a soft magnetic material, a nonmagnetic layer 93 made of a nonmagnetic material, a ferromagnetic layer 94 made of a ferromagnetic material, an antiferromagnetic layer 95 made of an antiferromagnetic material and a protective layer 96, the layers 92, 93, 94, 95 and 96 being stacked in this order on the underlying layer 91. Exchange coupling occurs on an interface between the ferromagnetic layer 94 and the antiferromagnetic layer 95, and thus the orientation of magnetization Mp of the ferromagnetic layer 94 is fixed in a fixed direction. On the other hand, the orientation of magnetization Mf of the soft magnetic layer 92 is freely changed in accordance with an external magnetic field.
A direct current is fed through the ferromagnetic layer 94, the nonmagnetic layer 93 and the soft magnetic layer 92 in the direction of a biasing magnetic field Hb, for example. This current is subjected to the resistance in accordance with a relative angle between the orientation of the magnetization Mf of the soft magnetic layer 92 and the orientation of the magnetization Mp of the ferromagnetic layer 94. Application of a signal magnetic field causes the change in the orientation of the magnetization Mf of the soft magnetic layer 92 and thus the change in electrical resistance of the spin valve film. The change in the resistance is detected as the change in a voltage. Recently, the greater a rate of resistance change (sometimes referred to as a rate of MR change) has been desired in order to allow magnetic recording at ultra-high density exceeding 20 gigabits per square inch.
A cited reference xe2x80x9cCoFe specular spin valves with a nano oxide layerxe2x80x9d, 1999 Digests of INTERMAG 99, published by May 18, 1999 reports that the rate of resistance change is improved by providing an oxide layer called an NOL layer for the ferromagnetic layer of the spin valve film.
Moreover, U.S. Pat. No. 5,408,377 discloses the spin valve film having the structure comprising the soft magnetic layer including therein a coupling layer (an AF coupling film) made of ruthenium (Ru) in order to increase the rate of resistance change. Furthermore, U.S. Pat. No. 5,828,529 discloses another spin valve film having the structure comprising the ferromagnetic layer including therein the coupling layer made of ruthenium.
However, there is no description about the material and film thickness of the oxide layer called the NOL layer in the above-described cited reference xe2x80x9cCoFe specular spin valves with a nano oxide layerxe2x80x9d, 1999 Digests of INTERMAG 99, published on May 18, 1999. Moreover, it is not clear the part of where the NOL layer is formed in the ferromagnetic layer.
Additionally, the improvement in the rate of resistance change is not given specifically and a relationship between the rate of resistance change and any other properties is not clear in U.S. Pat. Nos. 5,408,377 and 5,828,529.
The invention is made in view of the above problems. It is an object of the invention to provide a magnetic transducer and a thin film magnetic head which can increase a rate of resistance change and can also obtain good values of other properties.
A magnetic transducer of the invention comprises a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and capable of having two magnetizations oriented in opposite directions, and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein the ferromagnetic layer includes a ferromagnetic interlayer having magnetism and the ferromagnetic interlayer has higher electrical resistance than at least a part of the rest of the ferromagnetic layer.
In the magnetic transducer of the invention, the ferromagnetic layer has two magnetizations oriented in opposite directions, thereby reducing an influence of a magnetic field generated by the ferromagnetic layer upon the soft magnetic layer. Moreover, the electrical resistance of the ferromagnetic interlayer is higher than the electrical resistance of at least a part of the rest of the ferromagnetic layer. Thus, when a sense current flows through the magnetic transducer, the ferromagnetic interlayer reflects at least some electrons and thus limits a route by which the electrons move. As a result, the rate of resistance change is increased and thus even a low signal magnetic field can be detected. Furthermore, since the ferromagnetic interlayer has the magnetism, two portions in the ferromagnetic layer facing each other. across the ferromagnetic interlayer are magnetically integrated with each other.
The magnetic transducer of the invention can further adopt the following modes in addition to the above-described configuration.
In the magnetic transducer of the invention, it is desirable that a distance Dk1 between the nonmagnetic layer and the ferromagnetic interlayer is from 1.5 nm to 3 nm inclusive. Moreover, it is desirable that a thickness of the ferromagnetic interlayer is from 0.5 nm to 1 nm inclusive.
Desirably, the ferromagnetic layer includes an inner ferromagnetic layer, an outer ferromagnetic layer and a coupling layer sandwiched therebetween, and the inner ferromagnetic layer and the outer ferromagnetic layer are magnetically coupled to each other sandwiching the coupling layer. Such a configuration allows the ferromagnetic layer to have two magnetizations oriented in opposite directions. In this case, desirably, a relationship between the distance Dk1 between the nonmagnetic layer and the ferromagnetic interlayer and a distance Dk2 between the ferromagnetic interlayer and the coupling layer of the ferromagnetic layer is defined as 1.2xe2x89xa6Dk1/Dk2xe2x89xa63.
Additionally, the inner ferromagnetic layer may have a first inner ferromagnetic layer and a second inner ferromagnetic layer, and the ferromagnetic interlayer may be formed between the first inner ferromagnetic layer and the second inner ferromagnetic layer. In this case, desirably, the first inner ferromagnetic layer, the ferromagnetic interlayer, the second inner ferromagnetic layer, the coupling layer and the outer ferromagnetic layer are arranged in this order on the nonmagnetic layer. Such an arrangement allows limiting the route for the electrons to a particularly narrow range, thereby further increasing the rate of resistance change.
Desirably, a relationship between a thickness Tku1 of the first inner ferromagnetic layer of the inner ferromagnetic layer and a thickness Tku2 of the second inner ferromagnetic layer thereof is defined as 1.2xe2x89xa6Tku1/Tkusxe2x89xa63. Moreover, desirably, a relationship between the sum total of the thickness Tku1 of the first inner ferromagnetic layer, the thickness Tku2 of the second inner ferromagnetic layer and a thickness Tkn of the ferromagnetic interlayer and a thickness Tks of the outer ferromagnetic layer is defined as 1.2xe2x89xa6(Tku1+Tku2+Tkn)/Tksxe2x89xa63.
Furthermore, desirably, the soft magnetic layer includes an inner soft magnetic layer, an outer soft magnetic layer and a coupling layer sandwiched therebetween, and the inner soft magnetic layer and the outer soft magnetic layer are magnetically coupled to each other sandwiching the coupling layer.
The soft magnetic layer may include a soft magnetic interlayer having magnetism, and the soft magnetic interlayer may have higher electrical resistance than at least a part of the rest of the soft magnetic layer. In such a configuration, when the sense current flows through the magnetic transducer, the route for the electrons is further limited by the ferromagnetic interlayer in the ferromagnetic layer and the soft magnetic interlayer in the soft magnetic layer. Consequently, the rate of resistance change is further increased. In this case, desirably, the thickness of the soft magnetic interlayer is from 0.5 nm to 1 nm inclusive. Moreover, desirably, a distance Dn1 between the nonmagnetic layer and the soft magnetic interlayer is from 1.5 nm to 3 nm inclusive. Desirably, a distance Dn2 between the coupling layer and the soft magnetic interlayer of the soft magnetic layer is from 0.8 nm to 2.0 nm inclusive. Furthermore, desirably, a relationship between the distance Dn1 between the nonmagnetic layer and the soft magnetic interlayer and the distance Dn2 between the soft magnetic interlayer and the coupling layer of the soft magnetic layer is defined as 1.2xe2x89xa6Dn1/Dn2xe2x89xa63.
In addition, the inner soft magnetic layer may have a first inner soft magnetic layer and a second inner soft magnetic layer, and the soft magnetic interlayer may be formed between the first inner soft magnetic layer and the second inner soft magnetic layer. In this case, desirably, the first inner soft magnetic layer, the soft magnetic interlayer, the second inner soft magnetic layer, the coupling layer and the outer soft magnetic layer are arranged in this order on the nonmagnetic layer. Moreover, desirably, a relationship between the sum total of a thickness Tnu1 of the first inner soft magnetic layer, a thickness Tnu2 of the second inner soft magnetic layer and a thickness Tnn of the soft magnetic interlayer and a thickness Tns of the outer soft magnetic layer is defined as 0.35xe2x89xa6Tns/(Tnu1+Tnn+Tnu2)xe2x89xa60.70.
Another magnetic transducer of the invention comprises a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer and capable of having two magnetizations oriented in opposite directions, a ferromagnetic layer formed on the other surface of the nonmagnetic layer, and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein the soft magnetic layer includes a soft magnetic interlayer having magnetism and the soft magnetic interlayer has higher electrical resistance than at least a part of the rest of the soft magnetic layer.
In another magnetic transducer of the invention, the soft magnetic layer has two magnetizations oriented in opposite directions and thus an effective thickness of the soft magnetic layer is reduced. As a result, the rate of resistance change is increased. Moreover, the electrical resistance of the soft magnetic interlayer is higher than the electrical resistance of at least a part of the rest of the soft magnetic layer. Thus, when the sense current flows through the magnetic transducer, the soft magnetic interlayer reflects at least some electrons and thus limits the route for the electrons. As a consequence, the rate of resistance change is further increased. Moreover, since the soft magnetic interlayer has the magnetism, two portions in the soft magnetic layer facing each other across the soft magnetic interlayer are magnetically integrated with each other and therefore a coercive force is reduced.
Another magnetic transducer of the invention can further adopt the following modes in addition to the above-described configuration.
Desirably, the distance Dn1 between the nonmagnetic layer and the soft magnetic interlayer is from 1.5 nm to 3 nm inclusive. Moreover, desirably, the thickness of the soft magnetic interlayer is from 0.5 nm to 1 nm inclusive.
The soft magnetic layer may include an inner soft magnetic layer, an outer soft magnetic layer and a coupling layer sandwiched therebetween, and the inner soft magnetic layer and the outer soft magnetic layer may be magnetically coupled to each other sandwiching the coupling layer. Such a configuration enables the soft magnetic layer to have two magnetizations oriented in opposite directions. Moreover, desirably, the distance between the coupling layer and the soft magnetic interlayer of the soft magnetic layer is from 0.8 nm to 2.0 nm inclusive. Desirably, a relationship between the distance Dn1 between the nonmagnetic layer and the soft magnetic interlayer, and the distance Dn2 between the soft magnetic interlayer and the coupling layer of the soft magnetic layer is defined as 1.2xe2x89xa6Dn1/Dn2xe2x89xa63.
In addition, the inner soft magnetic layer may have a first inner soft magnetic layer and a second inner soft magnetic layer, and the soft magnetic interlayer may be formed between the first inner soft magnetic layer and the second inner soft magnetic layer. In this case, desirably, the first inner soft magnetic layer, the soft magnetic interlayer, the second inner soft magnetic layer, the coupling layer and the outer soft magnetic layer are arranged in this order on the nonmagnetic layer. Such an arrangement permits limiting the route for the electrons to a particularly narrow range, thereby further increasing the rate of resistance change. Desirably, a relationship between the thickness Tnu1 of the first inner soft magnetic layer and the thickness Tnu2 of the second inner soft magnetic layer is defined as 1.2xe2x89xa6Tnu1/Tnu2xe2x89xa63. Desirably, a relationship between the sum total of the thickness Tnu1 of the first inner soft magnetic layer, the thickness Tnu2 of the second inner soft magnetic layer and the thickness Tnn of the soft magnetic interlayer and the thickness Tns of the outer soft magnetic layer is defined as 0.35xe2x89xa6Tns/(Tnu1+Tnn+Tnu2)xe2x89xa60.70.
Furthermore, desirably, the first inner soft magnetic layer includes a nonmagnetic-layer-side layer close to the nonmagnetic layer and an interlayer-side layer close to the soft magnetic interlayer. Furthermore, desirably, the ferromagnetic layer includes a ferromagnetic interlayer having magnetism, and the ferromagnetic interlayer has higher electrical resistance than at least a part of the rest of the ferromagnetic layer.
Still another magnetic transducer of the invention comprises a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer, and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein the ferromagnetic layer has a first ferromagnetic layer, a second ferromagnetic layer, a third ferromagnetic layer, a magnetic interlayer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a nonmagnetic interlayer sandwiched between the second ferromagnetic layer and the third ferromagnetic layer.
A further magnetic transducer of the invention comprises a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer, and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein the soft magnetic layer has a first soft magnetic layer, a second soft magnetic layer, a third soft magnetic layer, a magnetic interlayer sandwiched between the first soft magnetic layer and the second soft magnetic layer, and a nonmagnetic interlayer sandwiched between the second soft magnetic layer and the third soft magnetic layer.
A thin film magnetic head of the invention has a magnetic transducer. The magnetic transducer comprises a ferromagnetic layer capable of having two magnetizations oriented in opposite directions, wherein the ferromagnetic layer includes a ferromagnetic interlayer having magnetism and the ferromagnetic interlayer has higher electrical resistance than at least a part of the rest of the ferromagnetic layer.
Another thin film magnetic head of the invention has a magnetic transducer. The magnetic transducer comprises a soft magnetic layer capable of having two magnetizations oriented in opposite directions, wherein the soft magnetic layer includes a soft magnetic interlayer having magnetism and the soft magnetic interlayer has higher electrical resistance than at least a part of the rest of the soft magnetic layer.
Still another thin film magnetic head of the invention has a magnetic transducer. The magnetic transducer comprises a ferromagnetic layer capable of having two magnetizations oriented in opposite directions, wherein the ferromagnetic layer has a first ferromagnetic layer, a second ferromagnetic layer, a third ferromagnetic layer, a magnetic interlayer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a nonmagnetic interlayer sandwiched between the second ferromagnetic layer and the third ferromagnetic layer.
A further thin film magnetic head of the invention has a magnetic transducer. The magnetic transducer comprises a soft magnetic layer capable of having two magnetizations oriented in opposite directions, wherein the soft magnetic layer has a first soft magnetic layer, a second soft magnetic layer, a third soft magnetic layer, a magnetic interlayer sandwiched between the first soft magnetic layer and the second soft magnetic layer, and a nonmagnetic interlayer sandwiched between the second soft magnetic layer and the third soft magnetic layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.